I love Bob Jackson's but that design is crap. They should be ashamed of themselves for putting that out to a consumer. In many/almost all instances you can get away with just using the canti's but if one was at speed and they exclusively used that centerpull hard, the leverage on that extension, over time, will cause it to fatigue and crack at/near the attachment of the fork. It is a cool looking bike though.*
*of course...........it's a Jackson